The present invention relates generally to a hydraulic shock absorber producing a vortex fluid flow therein for absorbing shock by resisting fluid flow therethrough. More particularly, the invention relates to a vortex flow shock absorber having relief means for relieving absorbing forces when the force produced by the shock absorber exceeds a predetermined value.
A hydraulic vortex-flow shock absorber is used, for example, in an automotive vehicle suspension for absorbing or damping road shock, rolling forces, pitching forces and so on. An absorber used with a vehicle suspension must provide not only sufficient absorbing force for stability of the vehicle but also respond gently enough not to give a rough ride. Therefore, the conventional vortex-flow shock absorber is provided with a relief valve for relieving excessive hydraulic pressure in order to prevent excessive absorbing force.
The relief valve of a conventional shock absorber is always subject to fluid pressure and must prevent the pressurized fluid from flowing therethrough while the fluid pressure is below the predetermined set pressure. Thus, the relief valve itself is necessarily stiff, which limits its response characteristics to fluid pressure greater than the set pressure. This may result in the maintenance of excessive pressure between the high pressure section and low pressure section due to insufficient relief effect. Furthermore, conventional relief valves open incompletely in response to a relatively high fluid pressure exceeding the set pressure which causes resistance to fluid flow therethrough due to an orifice effect. This unnecessarily increases the shock absorbing force and results in a rough ride.